Francis e



l 'KNOW ALL MEN EY THESE PRESENTS:

gleiten tatrs afmf @frn FRANCIS E. SESSIONS., OE WORCESTER, MASSACHUSETTS, ASSIGNOE To HIMSELE AND SAMUELA. KNOX.

Letters .Patent No. 75,986, dated iMarck 24, 1868.

dlgs Stimuli Infant in in tigers rttms patent mit mating 4in-tt nf tige tana.

That I, FRANCISv E. SESSI-ONS, of the city and county o f Worcester, and .Commonwealth of Massachusetts, have invented a certain new and useful vImprovement in the Process or Mode of Carbonizing and Hardening Iron 'and Steel; and I do hereby declare that the following is a full, clear, and exact description of the same, reference being had to the accompanying drawings, forming a part of this specification, in which- Figure Y1 represents a. steel mould board to a plough or cultivator, the pointbeing shown broken off, and turned around to show the fracture, and indicate the depth to which the metal has been carbonized and hardened by my improved process.

Figure 2 represents a similar mould-board, without the point being broken oh", and made in the ordinary-way.

Figure 3 represents aside view of a bar of' steel, marked B2, and also a longitudinal section of the same.

Figure 4 represents a side view ot' a bar of steel,`marked C3, and also a longitudinal section of the same.

Figure 5 represents a side view of a bar of steel, marked D, and alsoa longitudinal section of the same; and

Figure 6 represents a side view of a bar of common iron, marked E5, andalso a'longitudinalA section of the same. v

VThe sections are designed to illustrate by different shades of'color, the extent' to which the metal ofthe ends B, C, D, and E has been carbonized or hardened, as will be hereafter explained. v

To enable those skilled in the art to which my invention belongs to make and use the same, I will proceed to describe it more in detail. I l

'The piece of iron or steel, or the article made of iron or steel, to be carbonized or hardened, is first immersed in a bath of molten cast iron, rand allowed to remain the desired length of time, after which it is removed and thrown into cold water. I-have found that the melted cast iron, or bath of molten cast iron, works the best when heated to the degree required by founders for pouring good castings, and when thick orlarge pieces are to be earbonized'orhardened, it may be well to raise the heat of the molten metal still higher.

In the drawings, the steel mould-board, marked A, g. 1, after having been subjected to my process of carbonizing and hardening, above described, has a veryhard surface or shell, indicated by the dark color in the section, whilethe interior or central part ot" the metal, indicated by the light" color, remains tough and malleable, or nearly, if not quite, in the natural state in which it was when the mould was rst struck or formed from thesheetof steel. The shell a of the mould is so hard as to resist elfectually even the action of a good file. The steel bars, marked Bz'and 03,*at`ter having their ends B Gearbonized and hardened by my process, have similar shells, indicated by dark colors in the sections, While the central parts, indicated by the light colors, remain of the same or nearly .the same toughness as the `ends marked 2 and 3, which have not been suba jected to the process. The same is true ot' the end, E, ofthe iron bar marked E5, afterithas been subjected to the process, while the bar marked D4, which is'made of alittle higher grade of steel than the other bars, after being subjected to the same process, but allowed toremain in the molten bath .a short time longer, has its end, D, carbonized and hardened entirely through, as indicated by the dark shading in the section in tig. 5.

The depth atwhich the metal will be earbonized and hardened will depend much upon the length of time it is allowed to remain inthe molten bath of cast iron, and also somewhat upon the degree of heat to which.

the melted metal is raised, sothat each operator can by a few trials obtain almost any desired depth of carl bonization or hardness, whether operating upon iron or steel.

The bar or article, if instantly withdrawn from the molten bath, as soon as immersed,and plunged or thrown into cold water, will be carbronized or hardened to a slight `deptl1and which, in case of thin bars or articles made lfrom thin sheets of iron o r steel, may be all-sufiicient. l i

It is unnecessary to recapitnlate and en'umerate the advantages of my invention, since all, and especially workers in metal, willreadily appreciate the valu'e and extent to which :my invention may be applied successfully. Articles made from iron can be carbonized and hardened at a slight expense, so as to4 have a surface equal in resistance and hardness to the best tempered steel, while at the same time having an elasticity, 'owing' to the malleability and toughness of the central parts, which prevents the breaking or cracking of the articles, so that in many cases articles made from iron, and then carbonized and hardened byl my process, are

to similar articles made'from the best cztst steel by tlie G'minon oughs and cultivators; if mede of cust steel, they aireI i similar moulds made from ir'on and lowAgrndes of i on the wearing-surface as the best cast steel,

for superior, in a. practical point of vieu', modes of manufacture. For instance, take moulds for `pl liable to break, while they are expensive. By my process, steel can be carbonized and hardened'so'as to be quite as lmrrlup while at the salme time they can be bolted to the plough without danger ot' breaking or cracking, the central part being tough and malleable, so much so as to prevent the breaking of the article, even though deflected or K sprung to :xi-considerable extent. y

The above-cited case serves to illustrate the great practical utility of my-inve'ntion. Commoniron, after' having been carbonizedand hardened by my said process, can be heated in a. furnace, and then dran'n or hammeredinto any desired form, then tempered by the common mode of tempering steel, so tlm't'fthe best file will not act upon its surface. Y y

What I claim as new, and of my invention, and desire to secure by Letters Patent, is.-

The process above described for carbonizing and hardening iron and steel. l

' FRANCIS E.. SESSIONS.

Witnesses.:

Taos. H. Dones', 4 1). L. MILLER. 

